the Xbox 360 and PS3 are same-generation machines. One doesn't have additional effects over the other - 360 can do the same effects, just not as many of them simultaneously and with less geometry [because of the speed difference], but memory bottlenecks can kill part of the PS3 speed advantage anyway... the overall visual difference it makes will depend a lot on the developer's skill, and how much time and money the publisher spends on a game
full article here:
http://www.megagames.com/news/html/console/playstation3secretsrevealed.shtml
full article here:
http://www.megagames.com/news/html/console/playstation3secretsrevealed.shtml